#include <bits/stdc++.h>

#include <atcoder/all>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define FAST_IO                \
  ios::sync_with_stdio(false); \
  cin.tie(0);
const i64 INF = 1001001001001001001;
using Modint = atcoder::static_modint<998244353>;

i64 dijkstra(int K, vector<vector<pair<int, i64>>> &G) {
  int N = G.size();

  vector dist(N * K, INF);

  priority_queue<pair<i64, int>, vector<pair<i64, int>>, greater<>> pq;
  dist[0] = 0;
  pq.emplace(0, 0);
  while (!pq.empty()) {
    auto [d, x] = pq.top();
    pq.pop();
    int u = x / K;
    int k = x % K;

    if (d > dist[u]) continue;
    for (auto [v, w] : G[u]) {
      int nx = v * K + k;
      if (dist[nx] > d + w) {
        dist[nx] = d + w;
        pq.emplace(dist[nx], nx);
      }

      if (k + 1 < K) {
        nx = v * K + k + 1;
        if (dist[nx] > d) {
          dist[nx] = d;
          pq.emplace(dist[nx], nx);
        }
      }
    }
  }

  i64 ans = INF;
  for (int i = 0; i < K; i++) {
    ans = min(ans, dist[(N - 1) * K + i]);
  }
  return ans;
}

int main() {
  FAST_IO
  auto ans = 0LL;

  int N, M, K;
  cin >> N >> M >> K;
  vector<i64> C(M);
  for (auto &c : C) {
    cin >> c;
  }
  vector<int> u(M), v(M);
  for (int i = 0; i < M; i++) {
    cin >> u[i] >> v[i];
    u[i]--;
    v[i]--;
  }

  vector<vector<pair<int, i64>>> G(N);
  for (int i = 0; i < M; i++) {
    G[u[i]].emplace_back(v[i], C[i]);
    G[v[i]].emplace_back(u[i], C[i]);
  }

  ans = dijkstra(K + 1, G);
  if (ans >= INF / 2) {
    cout << -1 << endl;
    return 0;
  }
  cout << ans << endl;
}